The invention relates to dimensionally stable molded bone replacement elements made of mineral bone cement with residual hydraulic activity, a method and a set for producing it, as well as its use as a technical, bioengineering and/or pharmaceutical product, especially as an alloplastic bone implant.
Only a temporary retention of the implant material in the body is frequently required when medical implants are used. Research has been done for several years on the development of bioresorbable implant materials so that an elaborate operation to remove utilized implant materials that cannot be broken down by the body can be dispensed with in implantation processes of that type. Bioresorbable materials have the characteristic that they are gradually broken down after being implanted in the body. The decomposition products that arise in the process are reabsorbed by the body to a great extent.
Implant materials can be broken down actively or passively. In the case of an active breakdown by the organism, the implant material is broken down via enzymatic or cellular mechanisms. This applies, as an example, to implant materials made of collagen or mineral bone cements based on calcium phosphates. An active breakdown of implant materials is especially desired when the breakdown takes place within the framework of natural metabolism and not on the basis of an inflammatory reaction.
Previous solutions for providing alloplastic molded bone replacement elements are mostly based on calcium phosphates that are manufactured via precipitation or through high-temperature processes (sintering of suitable starting materials at temperatures >500° C.). Production through high-temperature processes does in fact supply materials with a substantial similarity to bone minerals, but it leads to a heavy coarsening of the structure; the bioactivity and resorbability of a molded bone replacement element are negatively impacted because of that.
Mineral bone cements that harden in situ via a hydraulic setting reaction are a special form.
U.S. Pat. No. 6,642,285 B1 discloses a hydraulic cement for manufacturing bone implants that is comprised of three components that are matched to one another, which are supposed to harden into a macro-porous solid immediately after mixing to the extent possible. The first component is a calcium source that completely hardens within 60 minutes as a preference in combination with an aqueous solution and a hydrophobic liquid; the product no longer has any hydraulic activity after hardening.
WO 2008 148 878 A3 discloses pastes, suspensions or dispersions comprised of a resorbable mineral bone cement component and a carrier liquid that are substantially free of water. The pastes, suspensions or dispersions that are disclosed have a liquid to pasty consistency and are implanted in this form as bone cements or bone replacement materials; the setting reaction completely takes place after implantation as a preference.
Lode et al. (J. Tissue Eng. Regen. Med. 2012) disclose that water-free, pasty preparations made of mineral bone cements can be printed via a printing process into porous molded elements that can subsequently be hardened into solid molded elements by putting them in aqueous solutions (to the extent described in the literature).
Surprisingly, it was found that molded elements that are manufactured in that way have especially good mechanical characteristics when the hardening does not take place in aqueous solutions, but instead in a saturated steam atmosphere at ambient temperatures or slightly increased temperatures (25-75° C.), especially below the sintering temperature.
The known solution suggestions have the situation in common that none of them involve residual hydraulic activity. Residual hydraulic activity is above all desirable based on biological conditions, because then part of the setting reaction of the cement-type mineral preparation takes place under biological conditions after implantation. Greater bioactivity can be achieved in this way.
Moreover, a stimulating effect on the osteogenic cells, which can be supported by an individualized adaptation to the bone defect of the patient, is desirable.
The instant invention is therefore based on the object of providing dimensionally stable molded bone replacement elements manufactured without using a ceramic-sintering step that are shaped under controlled conditions and that are solidified via a hydraulic setting process to the degree that adequate dimensional stability is ensured for storage, transport and the respective implantation conditions; the molded bone replacement elements are only completely hardened during and/or after the implantation, though.